Khazhismel Kumykov <[email protected]> writes: > On Thu, Dec 26, 2019 at 3:48 PM Gabriel Krisman Bertazi > <[email protected]> wrote: >> >> From: Bharath Ravi <[email protected]> >> >> Connection failure processing depends on a daemon being present to (at >> least) stop the connection and start recovery. This is a problem on a >> multipath scenario, where if the daemon failed for whatever reason, the >> SCSI path is never marked as down, multipath won't perform the >> failover and IO to the device will be forever waiting for that >> connection to come back. >> >> This patch performs the connection failure entirely inside the kernel. >> This way, the failover can happen and pending IO can continue even if >> the daemon is dead. Once the daemon comes alive again, it can execute >> recovery procedures if applicable. >> >> Changes since v2: >> - Don't hold rx_mutex for too long at once >> >> Changes since v1: >> - Remove module parameter. >> - Always do kernel-side stop work. >> - Block recovery timeout handler if system is dying. >> - send a CONN_TERM stop if the system is dying. >> >> Cc: Mike Christie <[email protected]> >> Cc: Lee Duncan <[email protected]> >> Cc: Bart Van Assche <[email protected]> >> Co-developed-by: Dave Clausen <[email protected]> >> Signed-off-by: Dave Clausen <[email protected]> >> Co-developed-by: Nick Black <[email protected]> >> Signed-off-by: Nick Black <[email protected]> >> Co-developed-by: Vaibhav Nagarnaik <[email protected]> >> Signed-off-by: Vaibhav Nagarnaik <[email protected]> >> Co-developed-by: Anatol Pomazau <[email protected]> >> Signed-off-by: Anatol Pomazau <[email protected]> >> Co-developed-by: Tahsin Erdogan <[email protected]> >> Signed-off-by: Tahsin Erdogan <[email protected]> >> Co-developed-by: Frank Mayhar <[email protected]> >> Signed-off-by: Frank Mayhar <[email protected]> >> Co-developed-by: Junho Ryu <[email protected]> >> Signed-off-by: Junho Ryu <[email protected]> >> Co-developed-by: Khazhismel Kumykov <[email protected]> >> Signed-off-by: Khazhismel Kumykov <[email protected]> >> Signed-off-by: Bharath Ravi <[email protected]> >> Co-developed-by: Gabriel Krisman Bertazi <[email protected]> >> Signed-off-by: Gabriel Krisman Bertazi <[email protected]> >> --- >> drivers/scsi/scsi_transport_iscsi.c | 63 +++++++++++++++++++++++++++++ >> include/scsi/scsi_transport_iscsi.h | 1 + >> 2 files changed, 64 insertions(+) >> >> diff --git a/drivers/scsi/scsi_transport_iscsi.c >> b/drivers/scsi/scsi_transport_iscsi.c >> index 271afea654e2..c6db6ded60a1 100644 >> --- a/drivers/scsi/scsi_transport_iscsi.c >> +++ b/drivers/scsi/scsi_transport_iscsi.c >> @@ -86,6 +86,12 @@ struct iscsi_internal { >> struct transport_container session_cont; >> }; >> >> +/* Worker to perform connection failure on unresponsive connections >> + * completely in kernel space. >> + */ >> +static void stop_conn_work_fn(struct work_struct *work); >> +static DECLARE_WORK(stop_conn_work, stop_conn_work_fn); >> + >> static atomic_t iscsi_session_nr; /* sysfs session id for next new session >> */ >> static struct workqueue_struct *iscsi_eh_timer_workq; >> >> @@ -1611,6 +1617,7 @@ static DEFINE_MUTEX(rx_queue_mutex); >> static LIST_HEAD(sesslist); >> static DEFINE_SPINLOCK(sesslock); >> static LIST_HEAD(connlist); >> +static LIST_HEAD(connlist_err); >> static DEFINE_SPINLOCK(connlock); >> >> static uint32_t iscsi_conn_get_sid(struct iscsi_cls_conn *conn) >> @@ -2247,6 +2254,7 @@ iscsi_create_conn(struct iscsi_cls_session *session, >> int dd_size, uint32_t cid) >> >> mutex_init(&conn->ep_mutex); >> INIT_LIST_HEAD(&conn->conn_list); >> + INIT_LIST_HEAD(&conn->conn_list_err); >> conn->transport = transport; >> conn->cid = cid; >> >> @@ -2293,6 +2301,7 @@ int iscsi_destroy_conn(struct iscsi_cls_conn *conn) >> >> spin_lock_irqsave(&connlock, flags); >> list_del(&conn->conn_list); >> + list_del(&conn->conn_list_err); >> spin_unlock_irqrestore(&connlock, flags); >> >> transport_unregister_device(&conn->dev); >> @@ -2407,6 +2416,51 @@ int iscsi_offload_mesg(struct Scsi_Host *shost, >> } >> EXPORT_SYMBOL_GPL(iscsi_offload_mesg); >> >> +static void stop_conn_work_fn(struct work_struct *work) >> +{ >> + struct iscsi_cls_conn *conn, *tmp; >> + unsigned long flags; >> + LIST_HEAD(recovery_list); >> + >> + spin_lock_irqsave(&connlock, flags); >> + if (list_empty(&connlist_err)) { >> + spin_unlock_irqrestore(&connlock, flags); >> + return; >> + } >> + list_splice_init(&connlist_err, &recovery_list); >> + spin_unlock_irqrestore(&connlock, flags); >> + >> + list_for_each_entry_safe(conn, tmp, &recovery_list, conn_list_err) { >> + uint32_t sid = iscsi_conn_get_sid(conn); >> + struct iscsi_cls_session *session; >> + >> + mutex_lock(&rx_queue_mutex); > This worried me a bit, but it seems we won't destroy_conn while it's > on the err list - cool. >> + >> + session = iscsi_session_lookup(sid); >> + if (session) { >> + if (system_state != SYSTEM_RUNNING) { >> + session->recovery_tmo = 0; >> + conn->transport->stop_conn(conn, >> + STOP_CONN_TERM); >> + } else { >> + conn->transport->stop_conn(conn, >> + >> STOP_CONN_RECOVER); >> + } >> + } >> + >> + list_del_init(&conn->conn_list_err); >> + >> + mutex_unlock(&rx_queue_mutex); >> + >> + /* we don't want to hold rx_queue_mutex for too long, >> + * for instance if many conns failed at the same time, >> + * since this stall other iscsi maintenance operations. >> + * Give other users a chance to proceed. >> + */ >> + cond_resched(); >> + } >> +} >> + >> void iscsi_conn_error_event(struct iscsi_cls_conn *conn, enum iscsi_err >> error) >> { >> struct nlmsghdr *nlh; >> @@ -2414,6 +2468,12 @@ void iscsi_conn_error_event(struct iscsi_cls_conn >> *conn, enum iscsi_err error) >> struct iscsi_uevent *ev; >> struct iscsi_internal *priv; >> int len = nlmsg_total_size(sizeof(*ev)); >> + unsigned long flags; >> + >> + spin_lock_irqsave(&connlock, flags); >> + list_add(&conn->conn_list_err, &connlist_err); >> + spin_unlock_irqrestore(&connlock, flags); >> + queue_work(system_unbound_wq, &stop_conn_work); >> >> priv = iscsi_if_transport_lookup(conn->transport); >> if (!priv) >> @@ -2748,6 +2808,9 @@ iscsi_if_destroy_conn(struct iscsi_transport >> *transport, struct iscsi_uevent *ev >> if (!conn) >> return -EINVAL; >> >> + if (!list_empty(&conn->conn_list_err)) > Does this check need to be under connlock?
My understanding is that it is not necessary, since it is serialized against the conn removal itself, through the rx_mutex, it seemed safe to do the verification lockless. It can only race with the insertion, in which case, it will be safely removed from the dispatch list here, under rx_mutex, and the worker will detect and skipped it. -- Gabriel Krisman Bertazi -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/open-iscsi/85ftgx7mlr.fsf%40collabora.com.
